How much do we know about Stonehenge? Less than we think. And what has Stonehenge got to do with the Ice Age? More than we might think. This blog is mostly devoted to the problems of where the Stonehenge bluestones came from, and how they got from their source areas to the monument. Now and then I will muse on related Stonehenge topics which have an Ice Age dimension...

THE BOOKSome of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- due for publication on June 1st 2018. After that, it will be available by post and through good bookshops everywhere. Bad bookshops might not have it....To order, click HERE

Thanks to Phil Morgan for drawing my attention to his contraption -- basically a rocking A-frame -- which was demonstrated last July at the Welsh Folk Museum at St Fagans, on a sort of experimental archaeology day.

There is a short writeup and photo on Andy Young's blog site.

You can see how it works -- the reinforced A-frame rocks on its base, and by pulling it forward you can drag along a sledge with a heavy weight (or a bluestone) by a few feet at a time. Then you reposition the rocker by pulling on the rear rope, and once it's in position you pull on the front rope again. And the sledge moves forward again. As Andy says, this might be practical for moving heavy stones on a building site -- but I would have serious doubts about the utility of the technique over a long distance, and in rough terrain.

Friday, 30 December 2011

A discussion on these famous "periglacial stripes" seems to be bubbling up again -- and purely by chance I came across these two pics -- from 1956 and 1958, I think -- from the excavations in the Avenue. The top photo shows the supposed periglacial features in cutting C48, and the lower photo shows what seems to be a cross-section of one of the stripes, as exposed in the side of cutting C40.

I don't recall ever seeing a plan or map of these features -- does anybody know of one?

The photos are from the Atkinson collection, on the EH web site.

For earlier discussions of these features, and some analogies from the Arctic, just type in "periglacial stripes" into the search box on this blog.

I had forgotten about this picture --it shows what Stone 60 was like in 1958 before the "cave" was filled with concrete in order to stabilize the stone. This is one of the Atkinson series, from the EH web site.

How depressing -- I suppose I must have looked a bit like that in 1958 -- except that I didn't smoke....

David Keys has drawn my attention to this piece published online on the Independent web site. It's a longer version of something we discussed on this blog a while ago. What interests me in particular is the "great pits" in the Cursus and the proposed link with the heelstone.

Extraordinary new discoveries are shedding new light on why Britain’s most famous ancient site, Stonehenge, was built – and when.

Current research is now suggesting that Stonehenge may already have been an important sacred site at least 500 years before the first Stone circle was erected – and that the sanctity of its location may have determined the layout of key aspects of the surrounding sacred landscape.

What’s more, the new investigation – being carried out by archaeologists from the universities’ of Birmingham, Bradford and Vienna – massively increases the evidence linking Stonehenge to pre-historic solar religious beliefs. It increases the likelihood that the site was originally and primarily associated with sun worship

The investigations have also enabled archaeologists to putatively reconstruct the detailed route of a possible religious procession or other ritual event which they suspect may have taken place annually to the north of Stonehenge.

That putative pre-historic religious ‘procession’ (or, more specifically, the evidence suggesting its route) has implications for understanding Stonehenge’s prehistoric religious function – and suggests that the significance of the site Stonehenge now occupies emerged earlier than has previously been appreciated.

The crucial new archaeological evidence was discovered during on-going survey work around Stonehenge in which archaeologists have been ‘x-raying’ the ground, using ground-penetrating radar and other geophysical investigative techniques. As the archaeological team from Birmingham and Vienna were using these high-tech systems to map the interior of a major prehistoric enclosure (the so-called ‘Cursus’) near Stonehenge, they discovered two great pits, one towards the enclosure’s eastern end, the other nearer its western end.

When they modelled the relationship between these newly-discovered Cursus pits and Stonehenge on their computer system, they realised that, viewed from the so-called ‘Heel Stone’ at Stonehenge, the pits were aligned with sunrise and sunset on the longest day of the year – the summer solstice (midsummer’s day). The chances of those two alignments being purely coincidental are extremely low.

The archaeologists then began to speculate as to what sort of ritual or ceremonial activity might have been carried out at and between the two pits. In many areas of the world, ancient religious and other ceremonies sometimes involved ceremonially processing round the perimeters of monuments. The archaeologists therefore thought it possible that the prehistoric celebrants at the Cursus might have perambulated between the two pits by processing around the perimeter of the Cursus.

Initially this was pure speculation – but then it was realized that there was, potentially a way of trying to test the idea. On midsummer’s day there are in fact three key alignments – not just sunrise and sunset, but also midday (the highest point the sun reaches in its annual cycle). For at noon the key alignment should be due south.

One way to test the ‘procession’ theory (or at least its route) was for the archaeologists to demonstrate that the midway point on that route had indeed a special relationship with Stonehenge (just as the two pits – the start and end point of the route – had). The ‘eureka moment’ came when the computer calculations revealed that the midway point (the noon point) on the route aligned directly with the centre of Stonehenge, which was precisely due south.

This realization that the sun hovering over the site of Stonehenge at its highest point in the year appears to have been of great importance to prehistoric people, is itself of potential significance. For it suggests that the site’s association with the veneration of the sun was perhaps even greater than previously realized.

But the discovery of the Cursus pits, the discovery of the solar alignments and of the putative ‘processional’ route, reveals something else as well – something that could potentially turn the accepted chronology of the Stonehenge landscape on its head.

For decades, modern archaeology has held that Stonehenge was a relative latecomer to the area – and that the other large monument in that landscape – the Cursus – pre-dated it by up to 500 years.

However, the implication of the new evidence is that, in a sense, the story may have been the other way round, i.e. that the site of Stonehenge was sacred before the Cursus was built, says Birmingham archaeologist, Dr. Henry Chapman, who has been modelling the alignments on the computerized reconstructions of the Stonehenge landscape

The argument for this is simple, yet persuasive. Because the ‘due south’ noon alignment of the ‘procession’ route’s mid-point could not occur if the Cursus itself had different dimensions, the design of that monument has to have been conceived specifically to attain that mid-point alignment with the centre of Stonehenge.

What’s more, if that is so, the Stonehenge Heel Stone location had to have been of ritual significance before the Cursus pits were dug (because their alignments are as perceived specifically from the Heel Stone).

Those two facts, when taken together, therefore imply that the site, later occupied by the stones of Stonehenge, was already sacred before construction work began on the Cursus. Unless the midday alignment is a pure coincidence (which is unlikely), it would imply that the Stonehenge site’s sacred status is at least 500 years older than previously thought – a fact which raises an intriguing possibility.

For 45 years ago, archaeologists found an 8000 BC Mesolithic (‘Middle’ Stone Age) ritual site in what is now Stonehenge’s car park. The five thousand year gap between that Mesolithic sacred site and Stonehenge itself meant that most archaeologists thought that ‘sacred’ continuity between the two was inherently unlikely. But, with the new discoveries, the time gap has potentially narrowed. Indeed, it’s not known for how long the site of Stonehenge was sacred prior to the construction of the Cursus. So, very long term traditions of geographical sanctity in relation to Britain’s and the world’s best known ancient monument, may now need to be considered.

The University of Birmingham Stonehenge area survey - the largest of its type ever carried out anywhere in the world – will take a further two years to complete, says Professor Vince Gaffney, the director the project.

Virtually every square meter in a five square mile area surrounding the world most famous pre-historic monument will be examined geophysically to a depth of up to two metres, he says.

It’s anticipated that dozens, potentially hundreds of previously unknown sites will be discovered as a result of the operation.

The ongoing discoveries in Stonehenge’s sacred prehistoric landscape – being made by Birmingham’s archaeologists and colleagues from the University of Vienna’s Ludwig Boltzmann Institute – are expected to transform scholars’ understanding of the famous monument’s origins, history and meaning.

You just need to click on the Geology Map viewer, and you can see either the satellite imagery of Britain (zoom in as close as you like), or a location map, or a composite image that incorporates the geology map at a maximum scale of 1:50,000. That's satisfactory for most purposes. Also, you can put your cursor on any point of interest and a label will come up which gives you the name of the geological formation at that point.

Amid all of the recent media frenzy relating to the Rhosyfelin paper (Ixer and Bevins 2011), Rob has encouraged us to concentrate on the paper itself rather than on the hype and nonsense appearing in sections of the media. That's fair enough, although as I have pointed out some of the hype and misunderstandings must be down to ambiguities in the press release which flagged up the importance of the paper to an outside world which has never been particularly well informed. So as a service to our faithful blogging community, not all of whom have access to the paper itself, I have escaped from the Christmas mayhem for a little while and -- while others snooze -- have had a good look through the article. I have copied a few key extracts at the base of this post. Some of the main points to come from the article are as follows:

1. At the Pembrokeshire end, 39 samples were investigated from the Pont Saeson - Brynberian - Crosswell area. Within this total, 12 were from Pont Saeson - Craig Rhosyfelin, collected in June 2011. A further 20 samples were collected in 1978. A further 7 samples were collected in 2010 by BJ, MPP and others. To be more specific, 19 out of the 39 samples were from Craig Rhosyfelin, and seven from Pont Saeson -- the area around SN 1158 3599 9 (near the bend in the river, about 200m SSE of the Rhosyfelin rocky spur ).

2. At the Stonehenge end, samples (an unspecified number) were analysed from excavations in the Stonehenge Avenue, Trench 44 and 45, the Aubrey Holes, from around the Heelstone, and the Darvill - Wainwright 2008 Stonehenge excavations. We don't know how many fragments from the Stonehenge layer were collected and how many were rejected. Neither do we know what proportion of the fragments were sarsen, or flint, or dolerite, or spotted dolerite, or other rock types, or rhyolite. We do not know how typical of the Stonehenge Layer the sampled areas actually are. So there is a strong bias in the collection of the samples. All we do know is that within the collection of RHYOLITE fragments from the sampled locations the link between those chips and flakes and the Craig Rhosyfelin outcrops seems to be strong.

3. The samples taken from near Pont Saeson appear to match very closely a rhyolite sample taken from the Cursus Field (Ixer and Bevins 2010).

4. The samples taken from Locality 8 near the tip of the Rhosyfelin rocky spur match very closely with two Stonehenge samples -- one fragment from near the Heelstone, and another from the Darvill-Wainwright 2008 excavation.

5. The four standing Stonehenge rhyolite bluestones numbered SH38, SH40, SH46 and SH48 do not match any of the rhyolites found at Pont Saeson or Rhosyfelin. However, some rhyolite fragments at Stonehenge do match standing stone SH48. Source unknown. Work is ongoing on these other rhyolites.

6. In the Pont Saeson - Craig Rhosyfelin area, the peculiar foliated rhyolites described in this paper seem to occur over an area of "a few hundred square metres."

7. There is a suggestion that orthostats SH46 and SH48 might match with lithic-crystal tuff outcrops lower down the valley and about 300m NW of Craig Rhosyfelin.

8. According to the authors, in excess of 99.9% of of the Stonehenge rhyolitic ‘debitage’ can be petrographically matched to the rhyolitic rocks found around Craig Rhosyfelin and Pont Saeson. It is largely because of that statement that the media have become obsessed with the idea that the source of the bluestones has now been found. However, as I have pointed out before on this blog, the >99.9% figure is meaningless, since we have no idea how many rhyolite fragments have been examined, how they were distributed in the Stonehenge Layer, how close together the collection points were, and what degree of selection was employed in the collection of samples during the respective digs. Percentage figures like this should never be used without a full presentation of the numerical data from which they are supposedly derived. In any case, we have no idea which rhyolites occur in the Stonehenge Layer in those large segments of Stonehenge that have not been excavated, and in the soils of the area around Stonehenge, and what their frequency may be.

9. There seems to be an assumption that the stump of orthostat SH32e could be an exact match with the samples from Locality 8 in the Rhosyfelin geological sampling exercise. However, we should bear in mind that no samples from that stump have been examined, and that the suggestion is based entirely upon an examination of the photographs in the Atkinson collection. Clearly some real science is needed on this matter........

10. I take issue with the authors over their suggestion that the narrowing down of rhyolite sources to a very small area, and in one case to within a few square metres, "is perhaps suggestive of human agency" in the transport of the bluestones. They argue that "a large number of different rock types from disparate areas" would suggest a glacial or "natural transport mechanism" -- but they imply that their research is not helpful to those who argue for glacial transport. They also seem to think that the "transport problem" now needs to be solved by archaeologists -- inevitably through a search for Neolithic quarries at Craig Rhosyfelin. I disagree with that too, as I have told Rob many times. In my view the problem needs to be solved by reference to glaciology and geomorphology.

My reading of the evidence presented? It looks as if this is a classic case of glacial entrainment, with rhyolitic and related rocks picked up by overriding ice from a stretch of the Afon Brynberian valley which is about 500m long and maybe 100m wide, from north to south. That's an area of 50,000 sq m. The provenancing of one or two of these rocks to a very small area on the ridge of Craig Rhosyfelin is an excellent and exciting geological development. It also appears that the stones from this locality (which may or may not have been orthostats or pillars) have been largely destroyed and redistributed as flakes or fragments -- although it may be that stump 32e is all that is left of one of them. In my view none of this work has any archaeological significance -- and it has no bearing on the bluestone transport debate. I can understand why Rob has reiterated several times on this blog that the transport issue is one that he treats with sublime indifference -- and assume that the hints about human agency were inserted into the paper in deference to the fact that it was published by an archaeological journal!

====================

SOME EXTRACTS

The local geology:

In the Pont Saeson area the Fishguard Volcanic Group
comprises a strongly foliated to foliated and lensoidal
rhyolitic rock the like of which is not seen elsewhere in
the outcrop of the group across the 32 km of strike section
from Pen Caer in the west to Crymych in the east. These
very distinctive rhyolitic rocks can be traced for no more
than 150 m from the northeasternmost end of Craig Rhosy-
felin. The foliation strikes quite consistently at between
040-050°, dipping to the northwest at between 40-80°
(Figure 2). Whilst the fabric is macroscopically typically
planar in thin section it can be seen to be lensoidal where
there are included, typically flattened, ovoid lithic clasts
which are usually 2 – 3 cm in maximum length (Figure
3), although larger elongate clasts up to 5 cm can be
located. These clasts are microtonalite. The main rock
is commonly traversed by thin (mm scale) quartz veins
which are tightly folded, with their folds being axial
planar to the foliation.

Field sampling:

Twelve accurately located in situ samples from Pont
Saeson (and especially Craig Rhos-y-felin) were collected
in June 2011. The sampling locations are shown in Figure
1. .... Polished sections were made of each of the twelve samples. These samples
augmented the original twenty in situ samples collected
by Bevins in 1978, during a reconnaissance study of the
Ordovician rocks of the Pont Saeson area. Due to this
the 1978 samples were not collected with the degree of
accuracy of the 2011 samples. These older samples are
provenanced therefore more generally at two locations
with grid references centred on SN 1166 3615 and SN
1158 3599. Additional samples from Craig Rhos-y-felin
collected by Mike Parker Pearson (2010) and Brian John
(2010) were also studied in order to be certain that the
full range of lithologies had been sampled.

In total thirty-nine lithics were investigated including nineteen from
Craig Rhos-y-felin and seven from the rhyolitic outcrops
centred on SN 1158 3599. Following a thorough
macroscopical description, detailed ‘total petrography’
as defined by Ixer (1994) and Ixer et al (2004) was
undertaken on the polished thin sections using both
transmitted and reflected light.

at the Stonehenge end:

These were compared with polished thin sections
of macroscopically similar rocks (groups A-D) from
the excavations of the Stonehenge Avenue, Trench 44
and 45, Aubrey Holes and the April 2008 Stonehenge
excavations.

----------------

Almost all (>99.9%) of the Stonehenge rhyolitic ‘debitage’
can be petrographically matched to rhyolitic rocks found
within a few hundred square metres at Pont Saeson and
especially to those found at Craig Rhos-y-felin. However,
it is possible in a few cases, where the petrography of
these Welsh in situ rocks is so distinctive, to suggest an
even finer provenance to within square metres, namely to
individual outcrops.

NB this statement:

One sub-crop, however, namely Craig Rhos-y-felin
Locality 8 appears to be the unique origin of the highly
distinctive Jovian fabric (an extreme combination of a
foliation with a strongly associated lensoidal fabric) seen
within some of the Stonehenge rhyolitic ‘debitage’. The
outcrop is situated at the extreme northeastern end of
Craig Rhos-y-felin.

Two Stonehenge samples have been matched with Craig Rhosyfelin Locality 8

Detailed collecting and identification of in situ rocks
from Pont Saeson and comparison with Stonehenge
material allows for a number of important conclusions.
The overwhelming majority of the Stonehenge rhyolitic
‘debitage’, namely that belonging to Groups A-C, can be
sourced from the Pont Saeson area and perhaps entirely
from Craig Rhos-y-felin, but from more than one site on
the crags.

The four standing Stonehenge orthostats SH38, SH40,
SH46 and SH48 offer no petrographical match for any
rhyolitic lithology at Pont Saeson.

In essence therefore Pont Saeson area may be the
dominant origin for the rhyolitic ‘debitage’ (Groups A-C)
but is eliminated as the source of any of the four standing
Stonehenge orthostats (SH38, SH40, SH46 and SH48).
It may be possible to go further. In 2011 Ixer and
Bevins stated that buried orthostat SH32e could also
originate from the Pont Saeson area and if that were so
“it would be the first non-preselite bluestone orthostat
to be precisely provenanced”. Examination of the Craig
Rhos-y-felin outcrops and comparison with photographs
of SH32e in excavation strengthens this belief and,
sometime when SH32e is re-examined and its foliation
described in detail, it should be possible to exactly match
the artefact to sub-crops at Craig Rhos-y-felin.

As importantly, the three macroscopically different
rocks (Groups A-C), originally assumed to have different
geographical provenances, are now shown to have a single
geographical origin. The number of discrete geographical
sources for the Stonehenge bluestones is of much
significance in the nature versus human transport debate,
with a large number of different rock types from disparate
areas supporting a natural transporting mechanism
whereas a restricted number of geographical origins is
perhaps suggestive of a human agency.

Ixer and Bevins (2010) declared that “The discovery of
the stilpnomelane lensoidal rhyolites is the first time that
a non-dolerite bluestone has been clearly provenanced, it
will not be the last”. It should be noted that the envisioned
provenance area was several hundreds of square metres.
This statement has proved to be correct and can now be
strengthened to state that ‘This is the first time that any
lithics from Stonehenge have been unequivocally assigned
to an area of a few square metres, namely to within a very
small single outcrop or couple of outcrops; it may not be
the last’.

It is now possible to attempt a focussed archaeological
examination of these restricted areas with some scientific
justification. These areas should include Locality 3 but
especially Locality 8 at the termination of Craig Rhosy-
felin.

Saturday, 24 December 2011

I thought this might be of interest. It's Bedd Arthur (the grave of King Arthur), near the tor called Carn Bica and not very far from Carn Meini. It's often referred to as a stone circle or even a stone oval -- but it's not really either of those. The standing stones of which it's built are very small, not much above knee height, and all of them seem to lean in towards the middle. I have always thought of it as a destroyed long barrow which might at one time have held a cromlech or burial chamber at its heart. I think those stones have been entirely removed -- unless they are buried beneath the turf. I think the remaining standing stones might have rested on the surface of the now-removed mound.

I'm not aware that this site has ever been excavated. It's not far from the "Neolithic tomb" excavated by TD and GW last summer, which was widely flagged up as having held the remains of the splendid fellow who drew up the plans for Stonehenge......

And while I am in geomorphology mode, here's another splendid pic from "Glaciers Online" -- if you look across the ice-covered bay towards the skyline, you'll see a magnificent "pseudo-moraine" near Cape Roberts, Antarctica. It's actually an ice-pushed ridge on the shoreline -- it must be an incredibly steep shoreline, with very deep water close inshore, because a tabular berg has come trundling in, breaking up the sea ice, and pushing up this considerable ridge of shoreline debris. If, after the passage of 20,000 years, somebody turns up here and assumes that this is a terminal moraine ridge, which marks the maximum extent of a glacial advance, he or she would very definitely be barking up the wrong tree.

In a spirit of goodwill at this Christmas season, and specially for Kostas, here is a splendid picture from the wonderful "Glaciers Online" web site. It shows a granite obelisk in the Victoria Dry Valley in Antarctica -- it couldn't have been put there by Neolithic tribesmen from Wiltshire, since nobody reckons that they strayed THAT far from home, no matter how good their coracles were, but I suppose it could have been put in place by a super-race of Emperor Penguins, who are known for their incredible achievements (David Attenborough and all that).

On the other hand we could go for the boring explanation and say that this isn't far from a glacier snout, and that this is an unusual morainic block projecting up from an extensive area of moraine which has (mostly) been covered at a later date by aeolian or windblown deposits. Very mundane. Sorry Kostas -- I couldn't find any nice pictures of blocks like this which are tastefully arranged in circles or rows......

Friday, 23 December 2011

I never thought I'd ever say this, but this appears to be quite a well-balanced report on the National Geographic web site.... and I like the bit about the sheep farm - makes it all sound very rural. And "it's official" ?!! What does that mean? Has HM Office of Provenancing now given the official seal of approval?

Apart from the inevitable over-simplification here and there, we can live with this.

It's Official: Stonehenge Stones Were Moved 160 Miles

Ancient bluestones match outcrop near Wales sheep farm, experts say.

Some of the volcanic bluestones in the inner ring of Stonehenge officially match an outcrop in Wales that's 160 miles (257 kilometers) from the world-famous site, geologists announced this week.
The discovery leaves two big ideas standing about how the massive pieces of the monument arrived at Salisbury Plain: entirely by human hand, or partly by glacier.
As it looks today, 5,000-year-old Stonehenge has an outer ring of 20- to 30-ton sandstone blocks and an inner ring and horseshoe of 3- to 5-ton volcanic bluestone blocks.
The monument's larger outer blocks, called the Sarsen stones, were likely quarried some 20 to 30 miles (32 to 48 kilometers) away in what's now England, where sandstone is a common material.
The origin of the bluestones, however, has weighed heavy on the hearts of archaeologists. Rocks resembling the material under a microscope haven't been found anywhere relatively near Stonehenge—at least until now.

[[ That of course is untrue -- we have all known since 1922 that many of the stones have come from the eastern Preseli area. It's the PRECISE provenancing that's new.....]]

Pinpointing the stones' origins is crucial to understanding how so many heavy hunks of rock made their way to the open plain where Stonehenge now stands.
"There's no way of explaining how these stones were transported without knowing where they came from," said study co-author Robert Ixer of the Univ of Leicester in the U.K.

Stonehenge Source Near Sheep Farm
For about two decades, Ixer and study co-author Richard Bevins, of the National Museum of Wales, have searched for the origins of the bluestones in outcrops around Wales.
As late as two years ago, the pair thought the blocks couldn't have come from the country—no samples from Welsh outcrops matched the Stonehenge blocks.
But not all of the samples collected over 20 years had yet been prepared for examination under a microscope. To be absolutely certain, the geologists began slicing up their remaining rocks.
The very first one—a chunk of rock collected in Wales 20 years ago—was a perfect match to the Stonehenge bluestones. The geologists spent the next two years checking a piece of Stonehenge bluestone against other outcrops around Wales.
"We sampled extensively and did not find anything that came anywhere close," Ixer said.
The rocky outcrop fingered by the duo's analysis is called Craig Rhos-y-Felin, which is now located on private land near a sheep farm.
The site is a long, bush-covered set of crags the size of four double-decker buses.

Next Step: Search for Tool Marks
The new find leaves two prominant theories for how the Welsh rocks got to Salisbury.
Humans could have quarried the site and dragged the blocks on wooden rafts. Or a giant glacier may have chiseled off the blocks and ferried them about a hundred miles (160 kilometers) toward Stonehenge, with humans dragging them the rest of the way.
If humans did the digging, archaeologists might detect marks left by tools or some other evidence. But if signs of human quarrying are lacking, the glacier idea might gain the upper hand.
"If we could find a quarry site," Ixer said, "we could tell if mankind was involved" in carving out the blocks.
But settling the issue, Ixer says, isn't up to geologists such as himself: "I have never betted in my life" and will not start now, he said.
"We need archaeologists. If they can show the rocks were quarried, that would suggest those rocks were transported by man."

[[We might add to that: "We also need geomorphologists. If they can show that the rocks were quarried by overriding ice, that would suggest that those rocks were transported by a glacier." It's interesting that the geologists hardly ever mention their earth science colleagues in this context, or admit that they have a real contribution to make. What was I saying about "geology in the service of archaeology"....?]]

Thursday, 22 December 2011

In the recent "exclusive" report of the Pont Saeson (Rhosyfelin) work, the Times reporter Norman Hammond quoted Rob Ixer as follows:

“The glacial theory is frozen out by this new evidence,” Dr Rob Ixer of Leicester University told The Times. If the stones had been transported east of the Bristol Channel by glacial action, a much wider range of sources would be expected. The pinpoint sourcing that has now been done argues strongly for human quarrying and transport of the bluestones.........."

That particular line has been used in headlines and as the underpinning of other media reports all over the world -- in the press, on TV and on radio, and in countless articles on the internet. Rob has not denied the quote attributed to him, and it's clear that this position is shared by Richard Bevins, who continues to speculate about the "Newport Bay route" for bluestone transport, and by other commentators like Mike Pitts, Mike Parker Pearson and Geoff Wainwright. On the telly the other night Mike Pitts more of less quoted the Times piece word for word -- and he has taken the same line on his own blog.

OK -- let's accept that the publication of an article like this will be trumpeted from the battlements by the authors and by their departmental media people. That's accepted -- everybody wants to be loved and famous! And of course the word "breakthrough" is over-used in such circumstances -- to demonstrate the value of a piece of work you have to "overturn" or "destroy" some pre-existing theory. And the handy theory that is supposedly destroyed in this case is the glacial transport theory -- add some nice metaphors, and away you go!

But let's stand back and look at this in the cold light of day. What has the new work actually done, with respect to the glacial transport theory? If anything, it enhances the theory rather than damaging or destroying it. My reasoning is as follows:

1. As I have said before, this is not a piece of archaeological work. It is a piece of straight geology -- an interesting and detailed exercise in provenancing. It's not a breakthrough at all, in the sense that since Herbert Thomas made the initial identification that many (not all) of the Stonehenge bluestones came from the Carn Meini area, there has been a gradual homing in on the precise locations from which the stones were taken, either by ice or human agency. The biggest leap forward was by the big Open University team project in the late 1980's, involving Olwen Williams-Thorpe, Rob Ixer and many others who used much more sophisticated techniques than were ever available to HHT around 1920. Geologists have been getting closer and closer to matching individual stones to individual outcrops in the field -- such is the way with science. There is a sort of continuum. And now we have the claim that much of the rhyolite debitage (NB -- not the TOTAL debitage) at Stonehenge can be traced to Rhosyfelin. No single stone has been provenanced with this accuracy -- we are just talking about lumps and chips found in the ground. The fact that the work is now reported in an archaeological journal is neither here nor there -- the work tells us NOTHING about how the stones were moved.

2. Some commentators on the new research (including senior academics) have suggested that the provenancing (or "pinpoint sourcing") of some fragments of Stonehenge bluestone to a POINT rather than a district somehow enhances the human transport theory and diminishes the glacial transport theory. That of course is utter nonsense, for the reasons given above.

3. While not diminishing or questioning the quality of the research by Rob and Richard, I have to say that I have read the paper carefully, and still have a few matters that cause me to feel uneasy. Because the paper was published in an archaeology journal, was it refereed by archaeologists rather then geologists? Perhaps the Editor will tell us -- because a paper like this should very clearly have been refereed by specialists in the same field as the authors. There are some other things that need to be said too. The "rhyolite debitage" referred to by the authors can only be the debitage that happens to have been examined (and collected) in assorted digs over the years -- the authors cannot know what lies beneath the surface in those parts of Stonehenge that have not been excavated. So there could be a strong bias at the Stonehenge end of this research. There could also be a strong bias at the Rhosyfelin end of the research. The authors claim to have tied down the "source area" for the foliated rhyolites to within a few metres -- but you can only make a statement like that if you can demonstrate that there is no chance that identical rocks are found elsewhere in the district. There are rhyolite outcrops in many different places in the Pont Saeson - Brynberian - Felin y Gigfran - Crosswell area. Some of them appear to be roughly on the same alignment as the sampled Rhosyfelin outcrop. Have ALL of those outcrops been sampled and eliminated as possible sources? Perhaps Richard can tell us.

4. Then there is this point: "If the stones had been transported east of the Bristol Channel by glacial action, a much wider range of sources would be expected." Come along now, chaps, let's get real. How many sources would you like? We are up to 32, at the moment, I think, and still counting....... and a point which is not often made is that all of the foreign stones that we know about in the "Stonehenge total assemblage" appear to have come from the west. That in itself is a persuasive argument for glacial transport.

5. Finally, let's look at the location from which the "destroyed foliated rhyolite orthostat" is supposed to have come. (One or more? It doesn't really matter.) It is in a river gorge, on the flank of a rocky spur where a smaller channel runs down into a larger one. A very difficult and constrained location. Why would anybody want to quarry large orthostats from a place like this, either from a practical standpoint or from a ritual one? You are just making enormous trouble for yourself -- since before you can do anything with your stones you have to get them up and away from this wretched river valley -- which would, by the way, also have been densely wooded during the Neolithic. The large hole in the ground which MPP and his team kindly opened up showed one large stone and many smaller stones, in exactly the positions where we would expect them to have accumulated over many years of rockfalls and scree development. But according to glacial theory this is one of many locations where, during the Ice Age, basal shearing could have occurred at the base of the Irish Sea Glacier as it flowed across the area. If there was shearing, there could also have been entrainment. I have gone over this many times before, so I'm not going to repeat it all again!

All in all, I cannot see any logical basis for the idea that the glacial transport theory has now been "frozen out" -- but I don't suppose that anything I say will halt or slow down the mad Quarry Hunt, since rational thought seems to be a thing of the past.

Wednesday, 21 December 2011

For those who might not have access to the original paper, I'm sure that Rob and Richard will not mind me sharing this image which shows the Craig Rhosyfelin sampling points which they used in their identifications of the foliated rhyolites:

I think I might have mentioned this one before, but the incredible application called "Where's the Path" allows you to examine the landscape in great detail, using the latest satellite imagery, and to view it on a split screen with the OS map to the left. You can choose what sort of images you want to look at, either side by side or full screen. And in some ways, most useful of all, your pointer on the screen is always given a precise grid ref (ten-figure) and geographical coordinates in a box at bottom right. This is the application which Rob Ixer and Richard Bevins used for fixing the locations of their Rhosyfelin sampling points.

You can zoom in and out of either image (right and left) and so the two images in the split screen do not always cover identical geographical areas -- but that does not matter greatly, because the cursor point is always in the right place, on both images. (And of course grid north is slightly different from true north.....)

Want a picture of Craig Rhosyfelin? What the hell -- this one of Carn Meini will do -- it's near enough, isn't it, and nobody will know anyway........

The "news" about the geological work at Craig Rhosyfelin (which readers of this blog knew about many months ago) has now been picked up by the global media, including papers in NZ, Australia and North America. For all I know, the story is also making the headlines in Japan and China........

It's great to have a real science story attracting attention, but I do wish that there would be a bit more respect for the things that Rob Ixer and Richard Bevins actually say in the article. All over the place we are having this story portrayed as "source of the Stonehenge bluestones (all of them) finally identified" -- and one article which I looked at actually seemed to suggest that all of the Stonehenge stones (including the sarsens) had now been fixed to a place of origin at Craig Rhosyfelin.

Even the august Today (BBC R4) programme this morning suggested that the origin of the bluestones (ie all of them) had now been narrowed down, and that from this point on all that needs to be done is for the quarry sites to be properly identified, and for the precise mechanisms of transport (rolling, sledging etc) to be worked out. Incompetence, from top to bottom.......

As for the Times headline thundering to the world that "the glacial transport theory has now been frozen out" -- that is total rubbish too, as I have pointed out. My thanks to Olwen Williams-Thorpe for sending a copy of a letter she submitted to the Times, making the same point. The letter may or may not have been published, but if it wasn't, it should have been:

Sir

Re: 'Bluestones glacier theory is now frozen out' Times 17/12/11

It is incorrect and misleading to suggest that new evidence on bluestone provenance 'freezes out' the glacial transport theory. Norman Hammond's article omits important information. There are many
bluestone rock types at Stonehenge that do not match the Pont Saeson outcrop. The arguments in favour of glacial transport therefore remain: varied bluestones, many sources, and glaciers capable of removing large erratics from Pont Saeson and other areas.

Dr Olwen Williams-ThorpeSenior Visiting Fellow of the Open University

====================

.............and now the ITV Ten O'Clock news caps the lot, with the most garbled report you are ever likely to see. First of all, they say that the new work relates to ALL of the Stones at Stonehenge, then they show a picture of Carn Meini and say it is Craig Rhosyfelin, and then they repeat the nonsense (with Mike Pitts's help) that the glacial transport theory is somehow diminished by the new evidence. Oh dear -- Richard and Rob, with the aid of your press release you have indeed unleashed a whirlwind of incompetent nonsense, which no doubt you could have prevented if you had worded things differently. What the hell -- who cares about the truth when there is a good story to be told?

According to Mr Blogger there have been 85,000 hits on the site now, so there must be a sizeable community of followers / occasional visitors out there. Thank you all for your interest and support, and above all else, for your contributions! So from me to you in this festive season:

Monday, 19 December 2011

On one of the discussion threads recently somebody said that it was impossible for morainic features to cross one another. Well, it's not impossible. I have seen morainic features that intersect, in response to shifting ice edge positions -- for example around the snout of a small glacier. Here is another interesting example from Bruarjokull in Iceland. What we have here is a fluted (ground moraine) feature running from the foreground and to the left of the girl, and crossing it at right angles is a crevasse fill -- typical of something that forms in a heavily crevassed and dirty glacier that is wasting rapidly. Neither of these features on the ground has anything to do with a previous ice edge position.

Also, notice the scatter of erratics in the background -- the definition on this pic is very good -- just click on it for enlargement.

Postscript

I'm not going to get sucked into one of those interminable exchanges with Kostas here, but as an aid to universal enlightenment here is a map of Wisconsin moraine positions in Illinois. Note that there are many intersections of moraines.

The reason for these intersections is that when an ice sheet edge is retreating across a landscape it is very rare for the whole ice edge to retreat at the same rate. Indeed, there may be short-lived advances during the course of an overall retreat. These small advances will of course have different dynamics in them -- and the ice streams may come from different directions from those of the earlier ice sheet. So moraines get truncated and overridden. Hence intersections. Perfectly simple.

The Times "exclusive" published the other day has now turned into a feeding frenzy, with all of the media getting in on the act. I wonder what the press release from the National Museum and Leicester Univ actually said? Anyway, another article, this time from the Daily Mail -- and another rubbish headline. Why can't reporters and sub-editors try to develop at least some respect for the truth? In the quote below Richard Bevins does at least acknowledge that there is a "glacial transport" theory out there, but why he keeps on referring to a "Nevern Estuary" human transport route as a possibility is beyond me, unless maybe he is just saying what the archaeologists want to hear.....

Quote: "Dr Bevins explains that his finding could help explain the method used to take the stones to Stonehenge and the reason, because the site is small enough for archaeologists to excavate to try and uncover evidence of human activity.He said: ‘It has been argued that humans transported the spotted dolerites from the high ground of Mynydd Preseli down to the coast at Milford Haven and then rafted them up the Bristol Channel and up the River Avon to the Stonehenge area.

‘However, the outcome of our research questions that route, as it is unlikely that they would have transported the Pont Saeson stones up slope and over Mynydd Preseli to Milford Haven. ‘If humans were responsible then an alternative route might need to be considered. However, some believe that the stones were transported by the actions of glacier sheets during the last glaciation and so the Pont Season discovery will need appraising in the context of this hypothesis.’

Shattered rockfall / scree debris beneath the rock outcrop at Craig Rhosyfelin. The "foliated rhyolites" here are claimed to match much of the rhyolite debitage at Stonehenge -- and Ixer and Bevins claim to be able to fix the source to within a few metres. Time will tell whether that claim is reliable or not.

Now the Independent has also reported on the Ixer / Bevins research, in a much more measured way. All in all, a pretty balanced report, apart from the headline, which should have read "Scientists discover one of many sources of rock used in Stonehenge's first circle." But I suppose that such a headline would have been deemed too boring...........

======================== Scientists discover source of rock used in Stonehenge's first circle

Scientists have succeeded in locating the exact source of some of the rock believed to have been used 5000 years ago to create Stonehenge's first stone circle.

By comparing fragments of stone found at and around Stonehenge with rocks in south-west Wales, they have been able to identify the original rock outcrop that some of the Stonehenge material came from.

The work - carried out by geologists Robert Ixer of the University of Leicester and Richard Bevins of the National Museum of Wales - has pinpointed the source as a 70 metre long rock outcrop called Craig Rhos-y-Felin, near Pont Saeson in north Pembrokeshire. It's the first time that an exact source has been found for any of the stones thought to have been used to build Stonehenge.

The discovery has re-invigorated one of academia's longest running debates - whether the smaller standing stones of Stonehenge were quarried and brought all the way there from Pembrokeshire by prehistoric humans or whether they had already been plucked out of ancient rock outcrops and carried all or part of the way to Wiltshire by glaciers hundreds of thousands of years earlier.

Archaeologists tend to subscribe to the 'human transport' theory, while some geomorphologists favour the glacial one. The debate is solely about Stonehenge's early/smaller standing stones (often known collectively as 'bluestones') - not about the larger ones (most of the so-called 'sarsens') which were incorporated into the monument several centuries later.

The Leicester University and National Museum of Wales scientists' discovery - reported in the journal, Archaeology in Wales - does not solve the mystery of how Stonehenge's Welsh-originating stones ended up in England, but it does potentially open up the possibility of finding archaeological evidence of quarrying activity that could indicate a human rather than a glacial explanation (indeed that archaeological search has already been launched by archaeologists from Sheffield and other universities). Conversely, any lack of such evidence would help those scholars arguing in the opposite direction. As the geological research continues, it's likely that numerous other rock outcrops in various parts of Pembrokeshire will be positively identified as sources of other stones used to build early versions of Stonehenge. Over past decades, the approximate area they came from has been identified - and the ongoing research will almost certainly succeed in pinpointing additional exact sources.

But although the stone fragments from Stonehenge will allow the scientists to track down where the material originally came from, those same fragments represent an altogether different mystery.

Literally thousands of fragments of rock - almost certainly from monoliths used at or around Stonehenge - have, over the years, been found in or near the world famous monument.

These fragments (mostly less than 50 grams each) appear to have been deliberately chipped off ancient monoliths at some stage in antiquity - many of them probably in the Neolithic.

However, most of the fragments examined so far are from particular types of rock which were used for less than 10% of the early (i.e. Welsh originating) Stonehenge monoliths. The fragments - found not just at Stonehenge itself but also elsewhere in the Stonehenge landscape - tend to be of a different geological character to the vast majority of early Stonehenge standing stones (which are mostly made of a different type of Pembrokeshire-originating rock). Indeed the rock type from Craig Rhos-y-Felin (just pinpointed by the new scientific research) was probably used for just one of the Stonehenge monoliths (a now buried stone, last seen in the 1950s).

This suggests that there may have been other stone circles or other 'standing stone' monuments in the landscape which have now vanished, but could in the future be found by other scientists (from Birmingham and other universities) who are carrying out an ongoing program of geophysical survey work throughout that landscape.

A further unsolved mystery is why prehistoric people were chipping fragments off probable monoliths. It's possible that they were chipped off in order to give monoliths a better shape. Alternatively, some monoliths or other rock material may have been broken up and re-cycled as stone axes - potentially imbued with particularly high status or conceivably perceived as having magical powers.

The detective work, that the University of Leicester and the National Museum of Wales scientists had to carry out to pinpoint the precise Pembrokeshire source of many of these fragments, was extremely complex.

First of all the geologists needed to sort through thousands of tiny fragments of Pembrokeshire-originating rock found by archaeologists at and around Stonehenge over the past 70 years.

Then the two scientists began to look particularly closely at around 700 of them which were made of a specific type of volcanically-originating rock (geologically, dating back some 460 million years) known as 'foliated rhyolite'.

They then succeeded in tentatively locating the approximate area of north Pembrokeshire which those 700 fragments originated from.

This was subsequently confirmed by comparing the chemical signature of tiny crystals (each one-five-hundredths of a millimetre in diameter) in the Stonehenge fragments with similar rocks in north Pembrokeshire.

Finally, by examining the detailed inter-relationships between minerals in samples from Stonehenge and north Pembrokeshire, they succeeded in pinpointing the precise rock outcrop.

If the stones were brought to Stonehenge from Pembrokeshire by human effort, the location of the newly discovered source (Craig Rhos-y-Felin) has interesting cultural implications.

For the newly discovered source is around five miles away from a wider area already known to have been the source for some of Stonehenge's other monoliths.

If humans were responsible for quarrying and transporting the stones from Pembrokeshire, then it would suggest that Stonehenge's Neolithic designers were extremely choosy and very specific as to where they got their stones from.

Research over recent years by Tim Darvill of Bournemouth University and Geoffrey Wainwright, a former chief archaeologist at English Heritage, suggests that the Pembrokeshire stones may have had a particular ideological or magical significance.

The outcrops where some of the stones come from are thought to have been associated with sacred springs and local Welsh stone circles.

It's argued that, by importing those particular rocks the 160 miles from Pembrokeshire to Wiltshire, the builders of Stonehenge thought they were taking possession of more than just plain rock. They may have regarded them as extremely important - and could even have seen them as possessing supernatural powers.

The newly discovered source is also significant because of its location. It lies on low ground to the north of the Preseli Mountains. This would have made transport to Wiltshire much more difficult than it would have been for other Pembrokeshire rocks used in Stonehenge and, known to have come from the High Preseli several miles to the south.

Transporting the north Pembrokeshire stones by sea would have required sailing round St. David's Head, a particularly difficult and dangerous route for a Neolithic boat. Alternatively the prehistoric quarrymen and their colleagues would have had to haul the stones over the top of the nearby Preseli Mountains. However, if humans took the stones to Stonehenge, it is also possible that the stones had already been used to construct circles in Pembrokeshire - and were therefore moved from those locations to Stonehenge, rather than from the original sources themselves.

Several times on this blog I have bewailed the fact that geomorphologists do not seem to be gainfully employed these days on archaeological projects -- especially on those relating to Stonehenge. Where are they? What are they doing if they are not doing this? Well, I suppose many of the brighter young geomorphologists (and glaciologists) these days are working on big projects related to global climate change -- and that's fair enough. But there are plenty of geomorphologists coming out of the UK universities with good degrees -- and an ability to make meaningful contributions to the archaeology projects currently under way.

Have any geomorphologists been employed on the recent MPP team digs at Craig Rhosyfelin, Garn Turne, Bluestonehenge, Cursus etc, and the TD/GW digs on the Preseli Hills and at Stonehenge? We hear occasional rumours about somebody with geomorphological expertise being "consulted" -- but these shadowy figures are hard to find, and it's even harder to find anything in the literature which they have directly contributed to some of the ongoing debates. Of course, even if they are getting stuck in on some of these digs, they will be acting as "geomorphologists in the service of archaeology" -- and will therefore be subject to exactly the same pressures as the "geologists in the service of archaeology" (like Rob and Richard) who currently publish in archaeological journals. Of course, I would never accuse them of bias, but if you are publishing in archaeological journals, with archaeologists as editors, and for a readership of archaeologists, of course you do what you can to enhance the chances of your papers being accepted and published. And that means a few hints here, a few conclusions there, that you might not have put in had the papers been submitted to straight geology journals.......... And without saying anything at all about the quality of the papers concerned, I wonder whether the editors of the journals concerned actually use GEOLOGISTS as referees prior to acceptance?

What we are talking about here is a very subtle process which gradually poisons the academic debate. If geomorphologists are absent from the process of putting together research applications, from the dig sites and from the definitions of fieldwork protocols etc, and from the evening discussions by the dig teams, then bias will be introduced at the very earliest stages of a project. That is why I was so appalled and disappointed by the Newport presentations by the team responsible for the Rhosyfelin dig -- it was clear to me (and others in the audience) that nobody had been present to challenge internally the ruling hypothesis that drove the whole team forward. So what we ended up with was a tidy and interesting dig but BAD SCIENCE. This refers:http://brian-mountainman.blogspot.com/2011/09/evening-of-fairy-tales.html
See my other posts on Craig Rhosyfelin also -- you can find them by using the search box.

So a word to archaeologists -- why aren't you employing geomorphologists on your digs? Are you really afraid that these guys might somehow disturb your comfortable convictions about the noble works of man? And a word to geomorphologists -- why aren't you getting involved in these big archaeology projects and seeking to convince project leaders that you have something to offer?

Sunday, 18 December 2011

A nugget of copper and other minerals found in the USA -- possibly from the Lake Superior area

We have had a lot of discussion on this site about the dark arts of provenancing "raw materials" found in archaeological contexts. There is, for example, a whole branch of archaeology devoted to the classification and provenancing of stone axes -- and as we have noticed, there is a tendency (tackled head-on by Stephen Briggs and a few others) to say that if stone axes of a certain lithology occur frequently in finds in the UK, then there must have been an axe factory at the place where this rock type is found in the landscape. This of course is wishful thinking more often than not, because genuine "quarries" or "axe factories" are incredibly difficult to find. And as Stephen and Olwen Williams-Thorpe have argued, where glaciation has affected the landscape, it is quite possible, and indeed probable, that the makers of axes have utilised whatever raw materials they discovered in erratic assemblages or even in deposits of till, for example exposed on river banks.

This all makes sense -- if a technology was widely known, it could have been employed in hundreds or even thousands of different locations, at the places where "raw materials" were discovered. There is no need for a centralised "production facility" where ore and nodules were mined, smelted and fabricated into implements. (But of course archaeologists search for these sorts of places all the time, because they allow a strengthening of assumptions about cultural uniformity and organization.)

The same argument applies with respect to the bluestones -- if they were "available" to the builders of a monument like Stonehenge in an erratic cluster or even in a scatter across an area of a few square miles, then obviously the instinct of the builders would be to use them -- in preference to anything found very far away.

There is a nice parallel discussion in Canada, where archaeologists have tended to assume that since Native American tribes used copper, and since copper ore is found in the ground around Lake Superior, then they must have mined the copper at the places of origin. Not necessarily so, say some geologists and archaeologists. Since copper nodules and lumps of ore (sometimes in large boulders) occur quite commonly in the glacial till and glacio-fluvial deposits further south, there is a strong chance that Native Americans simply used whatever they could find, maybe hundreds of kilometres away from the original source areas. So the heroic "trading" expeditions maybe never happened at all........

John Halsey has kindly allowed me to paste this message up onto the blog:

"I have only recently become aware of your support of the idea of glacial transport of bluestones. I would like to bring to your attention a "controversy" in North American archaeology that closely mirrors your interests, that is the transport of native copper nuggets and boulders from bedrock sources around Lake Superior to locations many hundreds of miles to the south. Acceptance of "drift" or "float" copper as it is commonly known, as legitimate sources of raw materials used by Native Amerficans to craft a wide variety of tools, weapons, and articles of decoration has been slow in coming. Many mainstream archaeologists continue to be fascinated with the idea of Argonaut-like voyages to strange and distant places to obtain this exotic material and discount the usage of drift copper as minor or non-existent. Attached is an expanded version of a paper I did seven years ago on the subject. I hope you find it of interest."

John R. Halsey, State Archaeologist of Michigan (retired). "Copper from the Drift."
(The paper is an enlarged version of a 2004 paper presented to various conferences in North America.)

Quote from RD Salisbury 1885:

The area over which copper is scattered is thus seen to be very great, perhaps not less than 450,000 square miles. If all the fragments came from Lake Superior, some of them must have been transported about 600 miles to the south, others, 150 or 200 miles, or perhaps more, to the west, and small specimens have been carried more than 100 miles east of the eastern limit of the locality from which the copper is supposed to have come. There is then an east-west distribution, accepting the testimony from Nebraska, of more than 700 miles, and a north-south distribution about 100 miles less (1885:47).

Quote from R Irving 1877:

Ancient implements of copper have been found very abundantly in Wisconsin...It is evident enough, however, that there is a direct connection between the abundance of copper implements, and the abundance of drift copper fragments, which in ancient times were probably much more plenty on the surface than now, and which by pounding could yield any and all of the implements ever found (1877:619-620).

Thanks to Tim for drawing my attention to these pieces -- the Times article (or some of it) and Mike Pitts's comments on his own site. I am amazed -- the work at Rhosyfelin does NOTHING to enhance the human transport theory, and it does NOTHING to increase the likelihood of Neolithic quarries being found. Have all of these people lost the capacity for rational thought? More on this in due course.....

If Rob is correctly quoted here, I am appalled. And if he is misquoted, I wonder what he proposes to do about it?

The long-running debate about the origin of the Stonehenge “bluestones” and how they got to Salisbury Plain some four millennia ago has taken another turn: a precise quarry source for much of the Stonehenge rock has been pinned down to a few square metres in southwestern Wales. This supports the notion that the bluestones were taken by human agency all the way from Pembrokeshire to Wiltshire, rather than helped along their way in the Ice Age by glacier transport.
“The glacial theory is frozen out by this new evidence,” Dr Rob Ixer of Leicester University told The Times. If the stones had been transported east of the Bristol Channel by glacial action, a much wider range of sources would be expected. The pinpoint sourcing that has now been done argues strongly for human quarrying and transport of the bluestones, whatever the motivation and precise route employed.........
Three major rock types and two minor ones can be identified within the “bluestone” range using both the entire stones and waste chips known as debitage which result from trimming the slabs on site at Stonehenge. The three major groups, originally thought to be from different geographical sources, can now be shown to be from the same locale.
The area of the new find lies at Pont Saeson on the northern flank of the Preseli Mountains, long known as the general source of the bluestones, some 6.5 kilometres (four miles) from Newport in north Pembrokeshire. The discovery follows the use of zircons included in the rocks to identify an area near Pont Saeson as one likely source of Stonehenge material by Dr Ixer and his colleague Dr Richard Bevins of the National Museum of Wales.
“Almost all — 99.9 per cent — of the Stonehenge rhyolitic ‘debitage’ can be petrographically matched to rhyolitic rocks found within a few hundred square metres at Pont Saeson and especially to those found at Craig Rhosyfelin.
“However, it is possible in a few cases, where the petrography of these Welsh in situ rocks is so distinctive, to suggest an even finer provenance to within square metres, namely to individual outcrops,” Ixer and Bevins report in Archaeology in Wales.
...
The outcrop itself is some 70 metres long and has many tall, narrow slabs up to two metres (6.5 feet) high as the dominant feature, splitting off from the parent rock and reminiscent of the Stonehenge bluestones. One of the Stonehenge shafts, known as SH32e, can be matched very closely to this outcrop, and must have been quarried there, not transported by a glacier.
....
The dispute over natural versus human transportation for these elements of an early and important phase of Stonehenge now seems to be settled —as Ixer says, the glacial theory is out cold.

Norman Hammond’s piece in Today’s Times (“Bluestones theory is now frozen out”) highlights the work by Richard Bevins and Rob Ixer on the precise origins of the Stonehenge bluestones. This is landmark stuff, and worth trying, briefly, to summarise.

There’s a lot of stone debris under the ground at Stonehenge, and more in the area around. For much of the 20th century the former was known as the “Stonehenge layer”. William Hawley associated it with the original dressing of megaliths (hence, any pits found below it were said to be older than the standing stones), while Richard Atkinson thought it derived from destruction of the stones, and was largely post-medieval or modern. As I found at my small excavation on the roadside in 1980, at least some of this debris almost certainly is prehistoric. At the time, I claimed it was contemporary with the carving of the stones. Mike Parker Pearson and Tim Darvill would now like to associate it with prehistoric stone destruction; on available evidence, I think it’s impossible to be certain either way. However, while the debris across the site is likely to have a variety of different origins, most of it, at least, probably does come from stones used for megaliths. So it’s an extremely important resource for understanding Stonehenge.

At last, we have some substantial modern studies of this material. Hammond quotes the most recently published, by Ixer and Bevins in Archaeology in Wales. Other articles include theirs in the Wiltshire Archaeological Magazine, and one they authored with Nick Pearce in the Journal of Archaeological Science (see references). They bring an important insight: the great bulk of the non sarsen stones at Stonehenge (but not all), come from a very restricted region in Pembrokeshire, south-west Wales. So restricted, that Ixer at least is confident in saying that this alone points to human transport as the only likely mechanism for the stones having got to Stonehenge.

The best known type of bluestone is the spotted dolerite, of which all the stones in the surviving inner arrangement at Stonehenge are composed. These are long known to have originated in the Preseli Hills. Ixer and Bevins have also examined specimens of the other main class, rhyolitic tuffs.

The work began principally with a study of the stone fragments picked up on the surface or excavated in test pits near the Cursus, just north of Stonehenge. Though several different types of rhyolitic rock were represented, they found that most “had a restricted and distinctive petrography both in terms of their mineralogy and textures”, and that “this petrography was unusual for south-west Wales, being only recognised from the Pont Saeson area”. In subsequent fieldwork, building on Bevins’s extensive knowledge of the area, they located outcrops at Pont Saeson, in a deep valley on the northern edge of the famous Preseli Hills. In the JAS article, they reported that some rhyolites from Stonehenge were the same as samples from Pont Saeson (on Craig Rhos-y-felin), and further detailed work confirming this is reported in the Archaeology in Wales article. The location is so precise, we have every reason to think that actual quarries should now be found, opening up exciting fieldwork possibilities.

Saturday, 17 December 2011

Craig Rhosyfelin, where the "precise quarry source" for the Stonehenge bluestones has been found, according to somebody who presumably knows about these things. So there we are then......

A little bird told me that there was an article in The Times today in which the glacial transport theory is definitively rejected on the basis of new geological evidence from a "precise quarry source" -- and that presumably means Craig Rhosyfelin. All I can find on the Times web site is what I have pasted below -- apparently it is in the Court and Social part of the Newspaper.... ??!!! Interesting, to say the least -- so this will be very scientific, then.

The Times wants to charge me for seeing the article in full, and I am disinclined to pay. If anybody has seen it, I'll be very interested to hear more....

...long-running debate about the origin of the Stonehenge “bluestones” and how they got to...precise quarry source for much of the Stonehenge rock has been pinned down to a few...motivation and precise route employed. Stonehenge’s “bluestones” are not the...

Friday, 16 December 2011

I'm often asked why, if the bluestones at Stonehenge are glacial erratics, they aren't covered with scratches (striations) and glacial facets which would demonstrate for all to see that they have been transported in or on glacier ice. Partly, that's because dolerite does not striate very easily -- it's very coarse, and because the component crystals are quite large, when glacial abrasion occurs on a dolerite surface the rock crumbles rather than becoming smooth. On the other hand rhyolite does smooth reasonably well, and I have seen striations on some ice-smoothed surfaces, on Carn Alw for example. But there is not a lot of rhyolite exposed above the surface at Stonehenge. Some sandstones can smooth and accept striations -- maybe the two sandstone stumps in the bluestone circle may give some clues as and when anybody gets to look at them. Ashes are sometimes too soft -- but given the right circumstances maybe we could find glacial scratches on the smoothed faces of some Stonehenge monoliths.

To give us some idea how complex are the effects of glacial transport on contained erratics, have a look at the boulder above. We dug it up last year from the thick till near our summer cottage in Sweden. This boulder has at least nine facets on it -- the seven that I have labelled, and two that we can't see. Number 1 probably shows the original shear face -- probably this boulder was sheared off the bedrock roughly along a weak contact between pink rock and bluish-grey rock. (I hesitate to give them names -- the pink rock is thought to have been Pre-Cambrian granite originally, but there has been tremendous metamorphism since it was originally emplaced. The bluish-grey rock is altered too.) You can click to seee the other facets more clearly -- they are all sheared or fractured faces of different ages. It's difficult to give them relative dates. Note that some are VERY rough, while others have been subject to varying degrees of abrasion and smoothing. The smoothest facet of all is Number 6 -- beautifully abraded, with very clear striations and also chatter-marks or pressure fractures created by tools being forced down onto the rock surface. If a tool is very big and the pressure exerted is very large too, then the whole boulder will be split or fractured, and thence reduced in size. And we will have another facet on the boulder. If this process goes on for long enough, the boulder is reduced to a collection of smallish bits and pieces, gravel and sand. If the boulder is protected, it can be carried for hundreds of kilometres without further modification.

This is typical of what happens to a boulder being carried at the base of a glacier. Boulders carried englacially or supraglacially are affected by a different set of processes.

The Stonehenge Bluestones

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Stonehenge and the Ice Age

The iconic ruin

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This Blog concentrates on matters relating to Stonehenge and the mystery of the bluestones. It is NOT an archaeology site, and I will try to keep all entries accurate and science-based. All comments are welcome, although I reserve the right to terminate discussions if I feel that they are getting nowhere! Also, please note that I will not accept Anonymous or "Unknown" posts -- the spam filters are set to dump those straight into the rubbish bin. So if you want to contribute, please use your name or a pen name.

About Me

I'm a native of Pembrokeshire. I read Geography at Oxford University prior to working in the Antarctic for a while and then I spent 11 years teaching geomorphology in Durham University. In 1976 I moved back to Wales with my wife and family to a smallholding -- where we set up two small businesses, my wife as a candle-maker and I as a writer and publisher. We have been at the same address now for 41 years. We couldn't live anywhere more beautiful. We have two sons and two grandsons. Apart from my great interest in Stonehenge and the bluestones, and local prehistory and folk traditions, I also write fiction -- and have now written eight volumes in the Angel Mountain Saga -- all tales about a feisty and imperfect heroine called Martha Morgan, who lived on the flanks of Carningli -- the mountain which lies between my home and the north Pembrokeshire coast.